1. Field of the Invention
The present invention generally relates to radiotherapy equipment and, more particularly, to a method and device for positioning patients with breast cancer in the prone position for imaging and radiation treatments.
2. Description of the Background
Breast cancer has become a global concern with over one million new cases reported annually. In the United States alone, the National Cancer Institute estimates that there will be about 200,000 new cases of breast cancer in 2009. Approximately twenty percent of these cases will result in fatalities.
Radiation therapy is an established method of treating patients with breast cancer especially when patients choose to conserve their breasts. When irradiating a breast, patient position bears an emerging concern. Currently most patients with breast cancer are treated in the supine (lying on the back) position, while the most sensitive and specific Magnetic Resonance Imaging (MRI) is performed in the prone (face down) position. Radiation treatment in the supine position only allows access from a few angles, and the supine position is also inferior due to the gravitational force, compressing the breast against the chest (which is compounded with large-breasted patients). In addition, breast motion resulting from breathing creates inaccuracies in locating the beam within the target volume.
Realizing the limitations of the supine position, imaging and treating patients with breast cancer from the prone position has been suggested by many researchers and physicians. With a patient lying on a patient support device or couch in the prone position, imaging or radiation therapy is implemented with the patient's breast pendent through an opening in the support device or couch. In the prone position, the breast tissue is pulled away from the chest wall by the gravitational force, which allows more access to the breast and reduces radiation exposure to the critical organs in the thorax (e.g., lung and heart). Another benefit of the breast radiation treatment in the prone position is that tumor targeting is more accurate by reducing the target motion associated with cardiac systole and respiratory movement. Many researchers have demonstrated that treating breast cancer by setting the patient in the prone position is more advantageous than in the conventional supine position.
One of the major issues of placing a patient in the prone position is that, once lying in the prone position, the patient losses the ability to move controllable distances for accurate positioning of her breast, especially when the patient is weak or overweight. When irradiating a tumor, it is very important to target it precisely. Unfortunately, due to difficulties in setting up patients in the prone position, both breast cancer screening and radiotherapy are more often performed in the supine position than in the prone position, although it more preferable to image and treat the breast in the prone position.
A number of patient positioning methods and devices have been developed in the past. U.S. Patent Application No. 20070036267 disclosed a patient positioning device to reduce skin radiation exposure when irradiating breast cancer in the prone position. The device employs a gas-filled bladder to spare the skin from receiving high radiation dose. U.S. Patent Application No. 19975609152 proposed a patient-supporting table for performing stereotactic mammographic biopsy procedures in the prone position. The table can pendently present a patient's breast in two different orientations with respect to the aperture. In U.S. Patent Application No. 20080201850, Brito et al. designed a patient positioning platform that allows a patient to lie in the prone position during breast imaging. The platform has a cushioned base to support the patient's torso and articulate head and arm rests. U.S. Patent Application No. 20070033735 provided a method and device for accurately and reproducibly positioning a patient's breast to receive radiation while the patient is in the prone position upon a radiation treatment table. The treatment table includes a generally flat patient support surface and a head positioning device. U.S. Pat. No. 5,564,438 proposed a method and apparatus for prone position radiation therapy of breast tissue. The apparatus effectively isolates the breast tissue to be irradiated from the rest of the body. U.S. Patent Application No. 20090064413 provided a patient support system to be used with a standard linear accelerator for prone position breast radiotherapy. The system allows access of the treatment beam to the breast from up to 360 degrees. U.S. Patent Application No. 20006047420 shows a head and upper body support system comprising three distinct supports. Each support has an inclined lower portion to support and lift the patient's abdomen and an upper portion to support the corresponding shoulder and the upper body. U.S. Patent Application No. 20056922859 proposed a patient positioning table for a medical procedure on a breast. The surface of the table can be adjusted to fit the shape of the patient's body. U.S. Patent Application No. 20080043905 disclosed a portable prone stereotactic mammography system for biopsies, image guided lumpectomies, and radiation treatment of breast. The system allows a physician to perform prone breast operations at any desired location. U.S. Patent Application No. 20026367104 disclosed a patient support method and apparatus for obtaining mammographic images. Using this method, the patient is placed in a left or right lateral decubitus position to present her breast to a mammography device. There are also commercially available prone breast boards or couches for facilitating breast treatments in the prone position. However, all these methods and devices cannot alleviate the difficulties in accurate patient positioning, which motivates the present invention, e.g., a novel method and device for precisely positioning patients with breast cancer in the prone position for imaging and radiation treatments.
The present invention allows easy and accurate patient setup in the prone position by using a double-layer couch with the top layer floating over the bottom layer for easily adjusting the position of the patient.